What is the function of a knob on the left under the steering wheel of JAC Ling Jun cab?

Hello, the knob on the left under the steering wheel of JAC Ling Jun cab is the indoor adjustment of headlights. If the road is steep uphill or downhill, the irradiation range of headlights at night will be far or near, which will not reach the ideal distance of drivers. At this time, it is necessary to fine-tune the headlights to achieve the ideal distance, and this function can be operated in the cab, which will make the driver's line of sight better and reduce the risk factor. This functional design is very user-friendly and easy to operate. I hope my answer can help you.